Hi,
I posted a message some time ago about the same problem with, apparently,
the same configuration (W98 and a 3DFX board).
As I suspected, it turns out that the problem does not come from Amaya
itself but rather from the board's driver. Downloading a new version from
http://www.3dfx.com (their current version is from january 2000) solved the
issue.
By the way I still have the "image-scrambled-syndrom" on the same machine,
with Linux and Amaya 3.0, even after upgrading to Redhat 6.2. All other
graphic applications work fine.
Cheers,
Serge Torres
Ecole normale superieure